console.log('app.ts-');
let a: number;
a = 33;

function fn(a: number, b: number){
    return a  + b
}

function fn1(this: Window){
    alert(this);
}

let box1 = document.getElementById("app")

if (box1){
    box1.addEventListener('click', function(){
        alert('点击了');
    })
}
